"Cory Booker has dedicated his life to the work of building hope and opportunity in communities where too little of either existed," Obama said in a Wednesday statement from Booker's campaign that ran in USA Today. "Whether as a college student working in East Palo Alto or as mayor of New Jersey's largest city, Cory has time and again taken on tough challenges, fought for the middle class and those working to join it, and forged coalitions that create progress — and that's the spirit he'll carry with him to Washington."

Sen. Frank R. Lautenberg, D-N.J., died in June, prompting a special election for his seat.